The Republican field of presidential candidates remains crowded. With 15 candidates still vying for the nomination, this episode of TestTube News takes a broad look at the party's vision and principles. Below, you'll find more info on where the two GOP candidates leading the polls, billionaire Donald Trump and retired neurosurgeon Ben Carson, stand on some of the most pressing issues of this presidential campaign.

Trans-Pacific Partnership

Carson recently came out in favor of the TPP, saying the massive trade agreement would further U.S. interests while curbing the influence of China in the region. Trump has slammed the deal, saying it will hurt American business and will do nothing to prevent country's like Japan from manipulating currency.

Taxes

At the core of Carson's tax policy is a 10 percent flat tax rate. Although the exact details have yet to be made public, Carson is basing his tax proposal on tithing-a Biblical concept that required everyone give one-tenth of their belongings to God. Trump's plan would raise taxes on the very wealthy, while reducing taxes for nearly everyone else. Anyone earning less than $25,000 per year would not pay any federal income tax under Trump's proposal.

Immigration

Recently, Carson outlined some broad points for his immigration policy. He would allow unauthorized immigrants currently living in the U.S. to register within a six-month period. Those who registered and had a "pristine record" would be eligible for some type of "guest worker" legal status. Those who did not register within the six-month time frame would be treated as criminals and likely deported. At one of the debates, Trump came out advocating for mass deportations of illegal immigrants, referencing "Operation Wetback," undertaken by President Eisenhower.

Health Care

Carson wants to repeal the Affordable Care Act, though, going against past statements, he would not get rid of Medicare or Medicaid. The details of his policy have yet to be made clear, but his health care plan is based on individuals having health savings accounts and paying for health care directly. Trump has not issued any specifics on his health care policy, though he has made it clear he would abolish the Affordable Care Act as well.